From: Dor Laor <dlaor@redhat.com>
To: Ronen Hod <rhod@redhat.com>
Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk
Date: Tue, 03 Jul 2012 17:28:12 +0300 [thread overview]
Message-ID: <4FF3017C.4020605@redhat.com> (raw)
In-Reply-To: <4FF3001C.9020706@redhat.com>
On 07/03/2012 05:22 PM, Ronen Hod wrote:
> On 06/18/2012 02:14 PM, Dor Laor wrote:
>> On 06/18/2012 01:05 PM, Rusty Russell wrote:
>>> On Mon, 18 Jun 2012 16:03:23 +0800, Asias He<asias@redhat.com> wrote:
>>>> On 06/18/2012 03:46 PM, Rusty Russell wrote:
>>>>> On Mon, 18 Jun 2012 14:53:10 +0800, Asias He<asias@redhat.com> wrote:
>>>>>> This patch introduces bio-based IO path for virtio-blk.
>>>>>
>>>>> Why make it optional?
>>>>
>>>> request-based IO path is useful for users who do not want to bypass the
>>>> IO scheduler in guest kernel, e.g. users using spinning disk. For users
>>>> using fast disk device, e.g. SSD device, they can use bio-based IO
>>>> path.
>>>
>>> Users using a spinning disk still get IO scheduling in the host though.
>>> What benefit is there in doing it in the guest as well?
>>
>> The io scheduler waits for requests to merge and thus batch IOs
>> together. It's not important w.r.t spinning disks since the host can
>> do it but it causes much less vmexits which is the key issue for VMs.
>
> Does it make sense to use the guest's I/O scheduler at all?
That's the reason we have a noop io scheduler.
> - It is not aware of the physical (spinning) disk layout.
> - It is not aware of all the host's disk pending requests.
> It does have a good side-effect - batching of requests.
>
> Ronen.
>
>>
>>>
>>> Cheers,
>>> Rusty.
>>> _______________________________________________
>>> Virtualization mailing list
>>> Virtualization@lists.linux-foundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
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>
next prev parent reply other threads:[~2012-07-03 14:28 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-18 6:53 [PATCH v2 0/3] Improve virtio-blk performance Asias He
2012-06-18 6:53 ` [PATCH 1/3] block: Introduce __blk_segment_map_sg() helper Asias He
2012-06-18 21:31 ` Tejun Heo
2012-06-19 2:02 ` Asias He
2012-06-19 18:00 ` Tejun Heo
2012-06-18 6:53 ` [PATCH v2 2/3] block: Add blk_bio_map_sg() helper Asias He
2012-06-18 6:53 ` [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk Asias He
2012-06-18 7:46 ` Rusty Russell
2012-06-18 8:03 ` Asias He
2012-06-18 10:05 ` Rusty Russell
2012-06-18 11:14 ` Dor Laor
2012-06-18 11:39 ` Sasha Levin
2012-06-19 2:51 ` Asias He
2012-06-19 6:21 ` Dor Laor
2012-06-20 4:46 ` Asias He
2012-06-21 9:49 ` Dor Laor
2012-07-01 23:54 ` Rusty Russell
[not found] ` <87r4svxcjw.fsf@rustcorp.com.au>
2012-07-02 2:45 ` Asias He
2012-07-02 6:41 ` Rusty Russell
2012-07-03 0:39 ` Asias He
2012-07-04 2:40 ` Rusty Russell
2012-07-06 1:03 ` Asias He
2012-07-03 13:31 ` Paolo Bonzini
[not found] ` <4FF2F417.2010209@redhat.com>
2012-07-03 14:02 ` Asias He
2012-07-03 14:22 ` Ronen Hod
2012-07-03 14:28 ` Dor Laor [this message]
2012-07-04 14:10 ` Paolo Bonzini
2012-06-18 21:28 ` Tejun Heo
2012-06-19 2:39 ` Asias He
2012-06-18 10:13 ` Michael S. Tsirkin
2012-06-19 2:21 ` Asias He
2012-06-18 9:37 ` Stefan Hajnoczi
2012-06-18 10:21 ` Michael S. Tsirkin
2012-06-18 10:45 ` Stefan Hajnoczi
2012-06-19 2:30 ` Asias He
2012-06-18 9:14 ` [PATCH v2 0/3] Improve virtio-blk performance Stefan Hajnoczi
2012-06-18 9:39 ` Asias He
2012-06-18 10:58 ` Stefan Hajnoczi
2012-06-19 4:24 ` Asias He
2012-06-19 10:14 ` Stefan Hajnoczi
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